1. Field of the Invention
The present invention relates to a data communication apparatus having a plurality of communication modes.
2. Related Background Art
A conventional apparatus of this type such as a facsimile system for performing image data communication has a plurality of communication modes such as GII, GIII, and GIV modes recommended by the CCITT (International Consultative Committee of Telephone and Telegram). In order to allow a source apparatus to communicate with a destination apparatus set in any mode, control protocols and a controller arrangement of the apparatus are inevitably complicated.
When a plurality of communication modes such as GII, GIII, and GIV modes are controlled by a single controller, control of the controller is complicated and a variety of control operations cannot be provided.
U.S. Pat. Appln. S.N. 823,286/1986 and S.N. 813,514/ 1985 disclose data communication apparatuses connected to a plurality of communication lines. One controller is used in each of these apparatuses and control operations of the controller are inevitably complicated.
In GII, GIII and GIV facsimile systems, different image data compression schemes (coding schemes and the like) are employed in the GII, GIII and GIV modes, respectively. When image data compressed according to different compression schemes are stored in one memory, the compression scheme of each of the differently compressed types of compressed data must also be controlled, and the controller is overloaded as a result.